Allocyclic Controls on Paleozoic Sedimentation in the Central Appalachian Basin
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U.S. DEPARTMENT OF THE INTERIOR U.S. GEOLOGICAL SURVEY ALLOCYCLIC CONTROLS ON PALEOZOIC SEDIMENTATION IN THE CENTRAL APPALACHIAN BASIN by C. Blaine Cecil1, David K. Brezenski2, and Frank T. Dulong1 Open File Report 98-577 This report is preliminary and has not been reviewed for conformity with the U.S. Geological Survey editorial standards (or with the North American Stratigraphic Code). Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Government. 'U.S. Geological Survey, Reston, VA 2Maryland Geological Survey, Baltimore, MD 1998 GEOLOGICAL SOCIETY OF AMERICA FIELD TRIP #4 OCTOBER 23-25, 1998 ALLOCYCLIC CONTROLS ON PALEOZOIC SEDIMENTATION IN THE CENTRAL APPALACHIAN BASIN TRIP LEADERS C. Blaine Cecil David Brezinski Frank Dulong FIELD TRIP GUIDE: C. Blaine Cecil David Brezinski Frank Dulong With contributions by: John Repetski Cortland Eble Nick Fedorko USGS Open File Report 98-577 FIELD TRIP STOPS Stop 1 Late Precambrian and early Cambrian strata, US Route 340, Weverton, MD. Stop 2 Early and middle Ordovician strata along the Chesapeake and Ohio Canal, Williamsport, MD. Stop 3 Devonian Keyser Limestone and Oriskany Sandstone, 1-68, Hancock, MD. Stop 4 Late Devonian and early Mississippian strata, 1-68, Sidling Hill, MD. Stop 5 Late Silurian strata, 1-68, Rocky Gap State Park, MD. Stop 6 Late Ordovician and early Silurian strata, Wills Creek water gap, Cumberland MD. Stop 7 Late Mississippian and Middle Pennsylvania strata at the Mississippian- Pennsylvanian Unconformity, 1-68, Savage Mt., MD. Stop 8 Late Devonian and early Mississippian strata, 1-68, Little Savage Mt., MD. Stop 9 Late Mississippian strata, Keystone Mine, Springs, PA. Stop 10 Middle Pennsylvania high alumina clay deposit, 1-68, Chestnut Ridge, WV. Stop 11 Mississippian-Pennsylvanian unconformity and early Middle Pennsylvania strata, 1-68, Chestnut Ridge, WV. Stop 12 Late Middle and early Late Pennsylvania strata, 1-68, west flank of Chestnut Ridge, WV. Stop 13 Late Pennsylvania paleosols, 1-79, Goshen Rd. exit, Morgantown, WV. Stop 14 Late Pennsylvania coal-bearing strata, Morgantown Mall, Morgantown WV. Abstract ALLOCYCLIC CONTROLS ON PALEOZOIC SEDIMENTATION IN THE CENTRAL APPALACHIAN BASIN C. Blaine Cecil, U.S. Geological Survey, Reston, VA 20192; (703)648-6415, fax 703-648- 6419, [email protected]; Frank Dulong, U.S. Geological Survey, Reston, VA 20192; (703)648-6416, fax 703-648-6419, [email protected] and David K. Brezinski, Maryland Geological survey, 2300 St. Paul St., Baltimore, MD, 21218-5210, phone (410) 554-5526 with contributions from John Repetski, U.S, Geological; Survey, Cortland Eble, Kentucky Geological Survey, and Nick Fedorko, West Virginia Geological and Economic Survey. This trip originates in Herndon, VA, near Washington D.C.'s Dulles International Airport and ends at the Pittsburgh International Airport, Pittsburgh, Pennsylvania. This trip will examine evidence for allocyclic controls on Paleozoic sedimentation and stratigraphy along an east-west transect across the Appalachian Basin from Washington's Dulles International Airport in northern Virginia to Pittsburgh International Airport in western Pennsylvania. Emphasis will be on variation in sediment supply as a function of long- to short-term paleoclimatic change. Relationships of climatic change to tectonic and eustatic processes will be discussed. Day one will include stops in strata that range in age from the Late Precambrian to the Early Mississippian. Ordovician and Silurian stops will include strata that primarily formed in response to Early Paleozoic aridity. Devonian and Mississippian stops will illustrate evidence for climatic controls on the origin of petroleum source rocks and reservoirs. The onset of the breakup of Pangea and Triassic rifting and climatically controlled rift basin cyclic sedimentation will also be illustrated during day one. Day two will illustrate climatic controls on Mississippian, Pennsylvanian, and Permian (?) sediment supply, and tectonic and eustatic controls on accommodation space. Factors that influenced the deposition of essentially coal-barren strata (Mississippian) and coal-rich strata (Pennsylvanian) will be a primary topic of discussion. The cyclic nature of Middle and Late Pennsylvanian coal occurrences, and the factors that influenced this cyclicity, will also be illustrated and discussed on day two. INTRODUCTION The objective of this field trip is to evaluate allocyclic controls (Beerbower, 1964), principally paleoclimate, on Paleozoic sedimentation and stratigraphy in the Appalachian foreland basin. The emphasis of the trip is to demonstrate long- to short-term paleoclimate change (Table 1) as a primary control on sediment supply, both chemical and siliciclastic (Fig. 1A and IB). Long-term climatic change as used herein is an estimated running average over time of variation in intermediate- to short-term climatic changes in rainfall. Interpretations of climate variation are based on paleoclimate indicators such as paleosols, sediment supply, sedimentary geochemistry and mineralogy, and paleontology. t t 81 41 NUMBER OF WET MONTHS NUMBER OF WET MONTHS WET: RAINFALL EXCEEDS EVAPOTRANSFORATION WET: RAINFALL EXCEEDS EVAPOTRANSPORATION ui tTa| H *l *I « >l 4| 6] (if *f «] »| (Of 111 n| NUMBER OF WET MONTHS NUMBER OF WET MONTHS WET* RAINFALL EXCEEDS EVAPOTRANSPORATIQN WET: RAiNFALL EXCEEDS EVAPOTRANSPORATION ENTJSOL AND IIMCEPT1SOL DRYSUBHUM1D I I HISTOSOL MOIST SUBHUMfD I I SEMlARtO HUMID SPODOSOL MOLLJSOL OXISOL ARID PERHOMK) AR!OIS( ALF1SOL ULTISOL 11" > r""*r~«"i'~«i ?T » ti 21al *i si «i 7| si » NUMBER OF WET MONTHS NUMBER OF WET MONTHS WET: RAINFALL EXCEEDS EVAPOTRANSPORATION WET: RAiNFALL EXCEEDS EVAPOTRANSPORATION Figure 1. A) Potential for fluvial siliciclastic load as function of climate; B) Potential for fluvial dissolved load as function of climate; C) Potential for peat formation as function of climate; D) Potential for eolian transport as a function of climate; E) Formation of USD A soil orders as a function of climate; and F) Climate classification based on the number of wet months per year. Field trip stops will examine Paleozoic strata that illustrate the sedimentary response to paleo-tropical rainfall regimes that ranged in duration from long-term to short-term (Table 1) and from arid to perhumid (Table 2, Figure IF). Tectonic and eustatic processes also are discussed at each Stop. These later two allocyclic processes, which have been studied, modeled, and are the subject of numerous publications and field trips, are most commonly considered to control sediment supply in contrast to climate which is generally not considered, As an example, a rapid flux of siliciclastic material into depocenters is generally attributed to tectonic uplift whereas siliciclastic sediment starvation is usually explained by sea-level rise, trapping sediments in estuaries. Basal sandstone units of the Cambrian, Silurian, Mississippian, and Pennsylvania in the Appalachian basin, are generally attributed to tectonically induced influx whereas laterally extensive shale deposits, such as the Ordovician Martinsburg shale and Devonian black shale units, are inferred to result from sediment trapping or autocyclic deposition of prodelta muds. Although tectonics clearly play a roll in uplift and subsidence, and eustasy contributes to accommodation space, variation in climate, particularly long- to short-term variation in rainfall in tropical conditions, is of greater importance as a control on sediment supply (e.g., Ziegler et al., 1987; Cecil, 1990 and references therein; Cecil et al. 1993). The trip stops illustrate that all three allocyclic processes, tectonics, eustatics, and climatics, require evaluation in order to understand and explain lithostratigraphy. Table 1. Tropical and subtropical climate change classification (modified from Cecil, 1990) RELATIVE CAUSE TIME DURATION (YEARS) Long-term Movement of continents 106-108 through latitudes; orogenesis 105-107 Intermediate-term 100 and 400 ka cycles 105 of orbital eccentricity Short-term Axial tilt and precession 104 cycles Very short-term not qualified 103 (millennial) Instantaneous Weather io-2 (weeks, days, hours) Table 2. Tropical climate regimes and degree of seasonally based on the number of consecutive wet months per year (modified from Thornthwaite, 1948). Number of wet months Climate regime Degree of seasonally 0 arid nonseasonal 1-2 semiarid minimal 3-5 dry subhumid maximum 6-8 moist subhumid medial 9-11 humid minimal 12 perhumid nonseasonal Many definitions of tropical climatic regimes are based on annual rainfall; few, however, attempt to incorporate seasonality (i.e., Thornthwaite, 1948). It is becoming increasingly apparent, however, that it is not the absolute amount of annual rainfall but the seasonality of annual rainfall that governs weathering, pedogenesis, erosion and sediment supply for a given catchment basin (e.g., Ziegler et al., 1987; Cecil, 1990). In order to assign degrees of seasonality, climate regimes, as used herein, are based on the number of wet months in a year. A wet month is defined as a month in which precipitation exceeds evapotransporation (Table 2, Fig. IF). By the limits set forth in Table 2 and Figure IF, both arid and perhumid conditions are nonseasonal. All other rainfall conditions have some degree of seasonality. Maximum seasonality and maximum fluvial siliciclastic sediment supply occur under dry subhumid conditions when there are three to five consecutive wet months (Fig. 1A). Maximum